What are vitamins?

Yes, indeed: What are vitamins? A good bit of investigation leaves me with the less-than-edifying notion that vitamins are collections of substances that do what vitamins do. For instance:

• Vitamins are organic nutrients.*
• They are (most usually) not single substances, but rather groups of compounds called vitamers.
• Vitamers are classified by their activity (i.e., what they do), not by their chemical structure.
• Etc.

Obviously, the whole thing needs to be fleshed out a bit. I’ll talk about some individual vitamins in the near future. Maybe that’ll help. Right?

* Others are protein, carbohydrates, and fat (the “macronutrients”, possibly to be talked about en masse later).